Electrical connectors such as modular plugs and jacks are commonly used as components in balanced twisted pair communications cabling reticulation networks. Applications include computer local area networks (LAN's) and telecommunications networks, where such connectors are typically used to connect terminal devices such as computers and telephone equipment to the building structured cabling system horizontal cabling.
One common type of modular connector used for such applications is the RJ45. International standards such as EIA-568-C.2 and ISO 11801 define the performance requirements for connectors used for balanced pair applications, and in particular for RJ45 connectors. The standards specify various levels of performance by category (e.g. Category 5e, 6 and 6A in particular). These requirements include high frequency transmission performance benchmarks, defined in terms of parameters such as near-end crosstalk (NEXT) and return loss (RL).
Crosstalk may be defined as unwanted signal coupling between one communications circuit and another adjacent circuit. It represents a form of interference between adjacent circuits and hence has a deleterious effect on circuit operation. The close physical spacing and layout of the conductors inside a balanced pair connector such as the RJ45 and the standardized requirements for cable pair leg assignments imply that undesirably high levels of crosstalk will be induced onto the circuits passing through the connector unless special measures are taken in the design of the connector to counteract it. When designing balanced pair connectors, a great deal of design effort is required to reduce the amount of crosstalk arising within the mated connector to a level which complies with the relevant standards requirements.
In order for an RJ45 connector to comply with the performance requirements of the international standards, the connector design must incorporate crosstalk compensation techniques. This is because an uncompensated jack, when mated with a plug, exhibits crosstalk characteristics which far exceed the limits imposed by the standards. In order to achieve standards compliance, a connector must not only compensate for crosstalk which arises within the jack, but also the very significant amount of crosstalk which arises in the plug. Since crosstalk increases with frequency, this becomes more important at the higher performance categories (e.g. Cat 6 and Cat 6A) because of the progressively higher frequencies involved and the more stringent standards requirements. Performance requirements are specified to 100 MHz for Cat 5e, to 250 MHz for Cat 6 and to 500 MHz for Cat 6A connectors. Thus any technique which reduces the amount of crosstalk which arises in the jack is considered very worthwhile, because it reduces the amount of crosstalk compensation required.
With early design connectors relatively simple capacitive crosstalk compensation measures were employed, and these were sufficient to achieve compliance with the performance requirements of the relevant standards at that time. As technology has advanced, however, computer network speeds have increased exponentially and the connector performance requirements have been commensurately tightened in the standards so as to reflect the more onerous network speed requirements. This has made it progressively more and more difficult to design a standards-compliant connector. Thus any aspect of connector design which improves a connector's transmission performance, or makes it easier for the installer to terminate or install is very worthwhile.
The purpose of an electric circuit is to contain a signal and guide it from the source to the receiver. At high frequencies, circuits act like transmission lines. All transmission lines have a property known as characteristic impedance. When signals travel along the transmission line, reflections are generated at points along the circuit where the circuit impedance differs from the line characteristic impedance. Reflections are undesirable on communications circuits because they represent a source of signal loss. On some types of circuits they can also cause interference back at the signal source. The return loss of a circuit provides a measure of the degree of impedance mismatch caused by such circuit impedance deviations or discontinuities. Due to its inherently unsymmetrical physical construction, a mated RJ45 connector represents a significant impedance mismatch when used at high frequencies in balanced pair circuits.
It is an object of the present disclosure to at least overcome some of the crosstalk and return loss problems associated with prior art electrical connectors.